1. Field of the Invention
The present invention relates to a method of and an apparatus for measuring cell rates at ATM (Asynchronous Transfer Mode) switching systems and subscribers to ATMLANs or the like, and more particularly to a method of and an apparatus for measuring peak rates of received cells.
2. Description of the Prior Art
Heretofore, cell rate measuring apparatus have measured all cell rates on lines with a single sliding window using the FIFO principle or the like.
FIG. 1 of the accompanying drawings shows the manner in which cell rates are measured by a conventional sliding window system which employs a single sliding window. In FIG. 1, a window size is of five cells. As shown in FIG. 1, the sliding window system counts cells that are contained in a window having a certain cell time length which includes all the cells that have been received thus far. The window itself slides as cells are received.
FIG. 2 of the accompanying drawings shows two different window sizes, the window size for effective cells 1 being of a 5-cell time and the window size for effective cells 2 being of a 10-cell time. As shown in FIG. 2, the starting ends of the windows are always aligned with each other, and only the terminal end of each of the windows differs depending on the window size. Since cells to be counted in windows are associated with the respective window sizes, it is necessary not to count the same cell twice in different windows.
It has been difficult for the conventional cell rate measuring apparatus to measure cell rates of various users which have various peak rates and rate distributions because there is only one sliding window width. It has been economically and technically problematic to install a plurality of measuring circuits for a plurality of sliding windows.